code: def _convert_string_aliases(deriv, target_shape):
      if isinstance(deriv, string_types):
          if deriv == "clamped":
              deriv = [(1, np.zeros(target_shape))]
          elif deriv == "natural":
              deriv = [(2, np.zeros(target_shape))]
          else:
              raise ValueError(
                  "Unknown boundary condition : %s" % deriv
              )
      return deriv
  
imports: from __future__ import division, print_function, absolute_import
  import functools
  import operator
  import numpy
  from scipy._lib.six import string_types
  from scipy.linalg import get_lapack_funcs, LinAlgError, cholesky_banded, cho_solve_banded
  from .None import _bspl
  from .None import _fitpack_impl
  from .None import _fitpack
label_desc: Use image node_id 6 for calling a global function with example usage: _convert_string_aliases(deriv, target_shape) and returns: deriv